Members of IMPACT, the country's largest public sector union, have narrowly failed to approve participation in next week's national strike.
The news is a setback to the Irish Congress of Trade Unions campaign of opposition to the Government's handling of the economy and the refusal of some employers to pay the national wage increases.
Under IMPACT's rules, a two-thirds majority in a ballot was required to sanction industrial action.
It is understood that while 65% of those balloted approved industrial action, that figure falls short of the 66% majority and is not enough to justify a strike.
The turnout was between 50% and 60%.
A spokesperson for IMPACT said that the vote did not necessarily mean that IMPACT members would not take part in Monday's strike.
The union's executive will meet tomorrow to examine the rule requiring the two-thirds majority to see if the executive has any discretion to approve the action.
All-out strike to disrupt airports
The national day of action, planned for a week from today, is likely to cause severe disruption at Dublin, Cork and Shannon airports.
SIPTU, which is joining the day of action, represents workers in the airports' fire, police and security services.
Unions are expected to serve notice of industrial action on behalf of thousands of workers today in protest at the failure of employers to comply with the national wage agreement.
Meanwhile, IBEC Director General Turlough O'Sullivan has urged unions to call off the planned action describing it as ‘entirely inappropriate’.
On RTÉ’s Morning Ireland, Mr O'Sullivan said a new national wage agreement was needed instead to deal with growing unemployment.
In his letter to ICTU General Secretary David Begg, Mr O'Sullivan said employers are extremely concerned by the vacuum in which Ireland finds itself ahead of the budget.
He says IBEC sees some merit in elements of ICTU’s ten-point plan for economic recovery and believes there is a basis for a joint accord on the way forward.
Mr O’Sullivan also warns that if the strike proceeds, the prospects for an accord would be seriously diminished.